Graphene supported catalyst, preparation method thereof and cyclododecatriene catalytic epoxidation method

Abstract

The invention relates to a graphene supported catalyst, a preparation method thereof and a method for catalyzing epoxidation of cyclododecatriene. The catalyst prepared by taking graphene and polyoxometallate as raw materials has excellent cyclic macromolecular catalytic activity; when the catalyst is used in the epoxidation reaction of macrocyclic olefin, the raw material conversion rate and the selectivity to a target product can be obviously improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a graphene supported catalyst, a preparation method thereof, and a method for catalytic epoxidation of cyclododecatriene. BACKGROUND

[0002] With the rapid development of science and technology, the epoxidation technology of macrocyclic olefins is constantly progressing and increasingly attracting attention. Among them, cyclododecatriene is one of the main macrocyclic polyenes produced in the petroleum chemical production process, is an important organic chemical raw material, and has a wide application prospect. The product obtained by epoxidation has high industrial value. The catalysts used in the existing technology for catalytic epoxidation of cyclododecatriene have the defects of low conversion rate and target product selectivity. SUMMARY

[0003] The purpose of the present disclosure is to provide a graphene supported catalyst, a preparation method thereof, and a method for catalytic epoxidation of cyclododecatriene, so as to improve the conversion rate and target product selectivity of the catalytic epoxidation of cyclododecatriene.

[0004] To achieve the above-mentioned purpose, the first aspect of the present disclosure provides a preparation method of a graphene supported catalyst, which comprises:

[0005] mixing graphene and polyoxometalate to obtain a mixture;

[0006] adding water to the mixture, and then placing it in a high-pressure reactor for reaction.

[0007] Optionally, the graphene is prepared by a supercritical carbon dioxide exfoliation method; and / or,

[0008] The D50 particle size of the graphene is 0.5-5 μm, the flake size is 1-10000 nm, the number of layers is 10 layers or less, and the specific surface area is 100-800 m 2 / g.

[0009] Optionally, the polyoxometalate is at least one selected from phosphotungstate, silicotungstate, phosphomolybdate, silicomolybdate, vanadotungstate and vanadomolybdate.

[0010] Optionally, the weight ratio of the graphene to the polyoxometalate is 100:(2-20).

[0011] Optionally, the weight ratio of the graphene to the polyoxometalate is 100:(5-15).

[0012] Optionally, the mixing conditions include: temperature 10-60℃, time 1-12h; and / or,

[0013] The reaction conditions include: temperature of 100-200℃, time of 2-24h.

[0014] In a second aspect, the present disclosure provides a graphene supported catalyst prepared by the method of the first aspect of the present disclosure.

[0015] In a third aspect, the present disclosure provides a method for catalytic epoxidation of cyclododecatriene, which comprises: contacting cyclododecatriene, an oxidizing agent, a solvent and a catalyst to perform an epoxidation reaction, wherein the catalyst is the graphene supported catalyst of the second aspect of the present disclosure.

[0016] Optionally, the weight ratio of the cyclododecatriene, the oxidizing agent, the solvent and the catalyst is 1:(0.5-10):(2-100):(0.1-2); and / or,

[0017] The reaction conditions include: temperature of 30-120℃, time of 1-24h.

[0018] Optionally, the oxidizing agent is one or more selected from the group consisting of hydrogen peroxide, tert-butyl hydroperoxide, phenethyl hydroperoxide, cumyl hydroperoxide, cyclohexyl hydroperoxide, peroxyacetic acid and peroxypropionic acid; and / or,

[0019] The solvent is one or more selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, tert-butyl alcohol, isobutyl alcohol, acetone, butanone and acetonitrile.

[0020] By the above technical solution, the present disclosure uses graphene and polyoxometalate as raw materials to prepare a catalyst, which has excellent catalytic activity for cyclic macromolecules. The catalyst is used in the epoxidation reaction of macrocyclic olefins, which is conducive to obtaining significantly improved raw material conversion rate and selectivity to the target product.

[0021] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments. DETAILED DESCRIPTION

[0022] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0023] In a first aspect, the present disclosure provides a preparation method of a graphene supported catalyst, which comprises the following steps S1-S2:

[0024] S1, mixing graphene and polyoxometalate to obtain a mixture;

[0025] S2, adding water to the mixture, and then placing it in a high-pressure reactor for reaction.

[0026] According to the present disclosure, in step S1, the graphene can be in the form of powder. In one embodiment, the graphene can have a D50 particle size of 0.5-5 μm, preferably 1-2.5 μm; a sheet size of 1-10000 nm, preferably 10-5000 nm; a number of layers of 10 or less, preferably 8 or less; and a specific surface area of 100-800 m2 / g, preferably 150-600 m2 / g. 2 2 / g.

[0027] In one preferred embodiment, the graphene is prepared by a supercritical carbon dioxide exfoliation method. The graphene powder prepared by the supercritical carbon dioxide exfoliation method has a more uniform particle size distribution and a smaller number of layers, which is beneficial to further improve the catalytic activity of the catalyst and the selectivity to the target product. Specifically, the preparation of the graphene can include: adding graphite into a reaction kettle, sealing the reaction kettle, introducing a gaseous intercalation medium (i.e., carbon dioxide) into the reaction kettle, and controlling the pressure in the reaction kettle at 1-200 atm by adjusting the amount of the gaseous intercalation medium, under the pressure and stirring conditions, the temperature of the system is raised to 25-500 °C to perform a molecular intercalation reaction for 0.1-24 h, after the reaction is completed, the pressure in the reaction kettle is rapidly reduced to half or less than half of the pressure in the reaction kettle within 0.1 s, and then the gas is released to normal pressure, the buffer tank is opened, and the graphene is obtained.

[0028] The polyoxometalate can be a heteropolyoxometalate and / or a homopolyoxometalate. The heteropolyoxometalate refers to a compound containing one or more heteroatoms and transition metal oxides, and its general formula can be NdXaMbOc; the homopolyoxometalate refers to a compound containing no heteroatoms and only the same transition metal oxides, and its general formula can be NdMbOc; wherein X represents a heteroatom such as P, Si, V, etc.; M represents a metal element such as Mo, W, V, Cr, etc. BIII-BV group elements; N can be selected from NH4, Na, K; O is an oxygen element; a, b, c, d represent the number of atoms or molecules, specifically, a = 1-4, b = 4-36, c = 6-60, d = 1-4.

[0029] ​In an embodiment, the polyoxometalate can be at least one selected from phosphotungstate, silicotungstate, phosphomolybdate, silicomolybdate, vanadotungstate and vanadomolybdate, preferably phosphotungstate and / or silicotungstate. The phosphotungstate can be, for example, potassium phosphotungstate, sodium phosphotungstate, ammonium phosphotungstate, etc.; the silicotungstate can be, for example, sodium silicotungstate, potassium silicotungstate, ammonium silicotungstate, etc.; the phosphomolybdate can be, for example, ammonium phosphomolybdate, potassium phosphomolybdate, sodium phosphomolybdate, etc.; the silicomolybdate can be, for example, sodium silicomolybdate, potassium silicomolybdate, ammonium silicomolybdate, etc.; the vanadotungstate can be, for example, ammonium vanadotungstate, potassium vanadotungstate, sodium vanadotungstate, etc.; and the vanadomolybdate can be, for example, sodium vanadomolybdate, potassium vanadomolybdate, ammonium vanadomolybdate, etc. The polyoxometalate can be a commercially available product or prepared by a method known in the art.

[0030] The ratio of the graphene to the polyoxometalate can be adjusted within a certain range. In an embodiment, the graphene and the polyoxometalate can have a weight ratio of 100:(2-20), preferably 100:(5-15).

[0031] The mixing conditions of the graphene and the polyoxometalate can include a temperature of 10-60°C, preferably 20-40°C, and a time of 1-12h, preferably 4-8h.

[0032] In step S2, the amount of water can be adjusted within a certain range. In an embodiment, the amount of water is an amount that allows the reaction system to reach a saturated state (i.e., saturated vapor) at the reaction temperature, and specifically, the mixture and the water can have a weight ratio of 1:(0.1-10), preferably 1:(0.2-6).

[0033] The reaction conditions can include a temperature of 100-200°C, autogenous pressure, and a time of 2-24h.

[0034] Further, the method can further include a step of drying the reaction product obtained after the reaction; and the drying conditions can be conventional conditions in the art.

[0035] The second aspect of the present disclosure provides a graphene-supported catalyst prepared by the method according to the first aspect of the present disclosure, which exhibits good catalytic activity and stability for cyclic macromolecules, and is used in catalytic oxidation of cyclic macromolecules such as macrocyclic olefins, and has high conversion rate and selectivity for target products.

[0036] In an embodiment, the graphene-supported catalyst contains 1-20 wt% of the polyoxometalate, preferably 5-15 wt% of the polyoxometalate, based on the total weight of the graphene-supported catalyst.

[0037] In a third aspect, the present disclosure provides a method for catalyzing epoxidation of cyclododecatriene (chemical formula: C 12 H 18 , CAS No. 16988-38-6), the method comprising: contacting cyclododecatriene, an oxidizing agent, a solvent, and a catalyst to perform an epoxidation reaction, wherein the catalyst is the graphene-supported catalyst according to the second aspect of the present disclosure.

[0038] Further, the weight ratio of the cyclododecatriene, the oxidizing agent, the solvent, and the catalyst can be 1:(0.5-10):(2-100):(0.1-2), preferably 1:(1-5):(5-50):(0.2-1).

[0039] The oxidizing agent can be one or more selected from hydrogen peroxide, tert-butyl hydroperoxide, phenethyl hydroperoxide, cumyl hydroperoxide, cyclohexyl hydroperoxide, peroxyacetic acid, and peroxypropionic acid, and is preferably hydrogen peroxide. The oxidizing agent can be in the form of an aqueous solution, and the concentration thereof can be, for example, 10-40 wt.%. The solvent can be water and / or a common organic solvent, and can be one or more selected from methanol, ethanol, n-propanol, isopropanol, tert-butyl alcohol, isobutyl alcohol, acetone, butanone, and acetonitrile.

[0040] The conditions of the epoxidation reaction can include a temperature of 30-120°C, preferably 60-100°C; autogenous pressure; and a time of 1-24 h, preferably 2-12 h.

[0041] The method of the present disclosure can effectively improve the conversion rate of raw materials and the selectivity of the target product 1,2-epoxy-5,9-cyclododecadiene (chemical formula: C 12 H 18 O). Specifically, the conversion rate of raw materials can reach more than 15%, and the selectivity of 1,2-epoxy-5,9-cyclododecadiene can reach more than 75%.

[0042] The present disclosure will be further described by way of examples, but the present disclosure is not limited in any way by the examples.

[0043] Example 1

[0044] (1) The graphene is prepared by supercritical carbon dioxide exfoliation method, specifically, 1 g of graphite is added into a reaction kettle, gaseous intercalation medium (carbon dioxide) is introduced into the reaction kettle, and the pressure in the reaction kettle is controlled at 1 atm by adjusting the gas inlet amount of the gaseous intercalation medium, under the stirring condition of the pressure and rotation speed of 200 rpm, the system temperature is raised to 200 ℃ to carry out molecular intercalation reaction, after 0.5 h of reaction, rapid pressure relief is carried out to rapidly reduce the pressure in the reaction kettle to half or less than half of the pressure in the reaction kettle within 0.1 s, then the gas is released to normal pressure, the buffer tank is opened, and 0.9 g of graphene powder is obtained, the D50 particle size of the graphene powder is 1.8 μm, the flake diameter is 870-1880 nm, the layer number is 3-8 layers, and the specific surface area is 221 m 2 / g.

[0045] (2) The graphene and sodium phosphotungstate (chemical formula Na3PW12O40) are mixed in a weight ratio of 100:12.6 and stirred and mixed at 30 ℃ for 4 h to obtain a mixture; after introducing an appropriate amount of water that can form saturated steam (the weight ratio of the mixture to water is 1:1) into the mixture, the mixture is sealed into a high-pressure reactor, and is subjected to closed reaction at 150 ℃ under autogenous pressure for 12 h, and the reaction product is dried to obtain the catalyst prepared in the example, and the polyoxometalate content of the catalyst is 11.2 wt%.

[0046] Example 2

[0047] The catalyst is prepared according to the method of Example 1, except that in step (2), the graphene and ammonium silicotungstate (chemical formula NH43SiW12O40) are mixed in a weight ratio of 100:15 and stirred and mixed at 40 ℃ for 5 h to obtain a mixture; after introducing an appropriate amount of water that can form saturated steam (the weight ratio of the mixture to water is 1:6) into the mixture, the mixture is sealed into a high-pressure reactor, and is subjected to closed reaction at 120 ℃ under autogenous pressure for 18 h, and the reaction product is dried to obtain the catalyst prepared in the example, and the polyoxometalate content of the catalyst is 13.0 wt%.

[0048] Example 3

[0049] The catalyst is prepared according to the method of Example 1, except that in step (1), the D50 particle size of the graphene powder prepared is 0.5 μm, the flake diameter is 560-2900 nm, the layer number is 3-6 layers, and the specific surface area is 310 m 2 / g. The polyoxometalate content of the catalyst prepared in the example is 11.2 wt%.

[0050] Example 4

[0051] The catalyst was prepared according to the method of Example 1, except that the graphene powder prepared in step (1) had a D50 particle size of 5 μm, a flake size of 2500-7000 nm, a number of layers of 6-10 layers, and a specific surface area of 115 m 2 / g. The catalyst prepared in this example had a polyoxometalate content of 11.2 wt%.

[0052] Example 5

[0053] The catalyst was prepared according to the method of Example 1, except that the graphene powder (purchased from Changzhou Sixth Element Material Science and Technology Co., Ltd., product number SE1233, prepared by the oxidation-reduction method) used in this example had a D50 particle size of 2.6 μm, a flake size of 2100-4300 nm, a number of layers of 2-6 layers, and a specific surface area of 242 m 2 / g. The catalyst prepared in this example had a polyoxometalate content of 11.2 wt%.

[0054] Example 6

[0055] The catalyst was prepared according to the method of Example 1, except that the weight ratio of graphene to sodium tungstophosphate prepared in step (2) was 100:20. The catalyst prepared in this example had a polyoxometalate content of 16.7 wt%.

[0056] Example 7

[0057] The catalyst was prepared according to the method of Example 1, except that the weight ratio of graphene to sodium tungstophosphate prepared in step (2) was 100:2. The catalyst prepared in this example had a polyoxometalate content of 1.96 wt%.

[0058] Comparative Example 1

[0059] This comparative example used graphene according to Example 1 as the catalyst.

[0060] Comparative Example 2

[0061] This comparative example used a tungstophosphorus heteropolyoxometalate (chemical formula Na3PW12O40) as the catalyst.

[0062] Test Example

[0063] The catalysts of the examples and comparative examples were used to carry out catalytic epoxidation of cyclododecatriene, and the specific steps were as follows: under the protection of nitrogen, cyclododecatriene, 30% by weight of peroxyl hydrogen, methanol and catalyst were added into a 250 mL volume Parr reactor in a weight ratio of 1:5:25:1, and after sealing, the stirring was opened, and the epoxidation reaction was carried out at 50°C and autogenous pressure for 6h. After the reaction was completed, the reaction product was distilled under reduced pressure, the product was collected, and the composition of the product after the reaction was analyzed by distillation, crystallization and weighing, and the conversion rate of cyclododecatriene and the selectivity of the target product 1,2-epoxy-5,9-cyclododecadiene were calculated according to the following formula, and the results are shown in Table 1.

[0064] Cyclododecatriene conversion rate = (weight of cyclododecatriene input - weight of cyclododecatriene left after reaction) / weight of cyclododecatriene input x 100%

[0065] 1,2-epoxy-5,9-cyclododecadiene selectivity = (weight of 1,2-epoxy-5,9-cyclododecadiene in the product / total weight of the product) x 100%

[0066] Table 1

[0067] Cyclododecatriene conversion / % 1,2-Epoxy-5,9-cyclododecadiene selectivity / % Example 1 26.3 81.6 Example 2 20.5 78.3 Example 3 17.8 80.2 Example 4 16.4 79.3 Example 5 15.0 75.2 Example 6 15.7 77.9 Example 7 15.1 76.5 Comparative Example 1 <0.1 <5.0 Comparative Example 2 6.3 24.5

[0068] As can be seen from Table 1, the catalyst provided by the present disclosure has high raw material conversion rate and target product selectivity in the cyclododecatriene epoxidation reaction.

[0069] The above describes the preferred embodiments of the present disclosure, but the present disclosure is not limited to the specific details in the above embodiments, and various simple modifications can be made to the technical solutions of the present disclosure within the technical concept of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0070] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present disclosure will not further describe various possible combination manners.

[0071] In addition, various different embodiments of the present disclosure can also be combined in any manner, as long as it does not deviate from the idea of the present disclosure, and it should be considered as disclosed by the present disclosure.

Claims

1. A method for preparing a graphene-supported catalyst, characterized by, The method comprises: mixing graphene and polyoxometalate to obtain a mixture; adding water to the mixture, and then placing the mixture in a high-pressure reactor to perform a reaction.

2. The method of claim 1, wherein, The graphene is prepared by a supercritical carbon dioxide exfoliation method; and / or, The D50 particle size of the graphene is 0.5-5 μm, the flake size is 1-10000 nm, the number of layers is 10 or less, and the specific surface area is 100-800 m 2 / g.

3. The method of claim 1, wherein, The polyoxometalate is at least one selected from phosphotungstate, silicotungstate, phosphomolybdate, silicomolybdate, vanadotungstate and vanadomolybdate.

4. The method of claim 1, wherein, The weight ratio of the graphene to the polyoxometalate is 100:(2-20).

5. The method of claim 4, wherein, The weight ratio of the graphene to the polyoxometalate is 100:(5-15).

6. The method of claim 1, wherein, The mixing conditions include a temperature of 10-60℃ and a time of 1-12h; and / or, The reaction conditions include a temperature of 100-200℃ and a time of 2-24h.

7. A graphene-supported catalyst prepared by the method of any one of claims 1-6.

8. A process for the catalytic epoxidation of cyclododecatriene, characterized in that, The method comprises: contacting cyclododecatriene, an oxidizing agent, a solvent and a catalyst to perform an epoxidation reaction, wherein the catalyst is the graphene-supported catalyst of claim 7.

9. The method of claim 8, wherein, The weight ratio of the cyclododecatriene, the oxidizing agent, the solvent and the catalyst is 1:(0.5-10):(2-100):(0.1-2); and / or, The epoxidation reaction conditions include a temperature of 30-120℃ and a time of 1-24h. The oxidizing agent is one or more selected from hydrogen peroxide, tert-butyl hydroperoxide, phenethyl hydroperoxide, cumyl hydroperoxide, cyclohexyl hydroperoxide, peroxyacetic acid and peroxypropionic acid; and / or, 10. The method of claim 8, wherein, The solvent is one or more selected from methanol, ethanol, n-propanol, isopropanol, tert-butyl alcohol, isobutyl alcohol, acetone, butanone and acetonitrile. ​